This application claims the priority of German Application No. 103 18 304.3 filed Apr. 14, 2003, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a supporting disc for a supporting disc bearing for open-end spinning rotors, comprising a disc-like base body having on its outer circumference a tire-like covering as well as a front side, in which a cylinder-shaped permanent magnet is inserted in a through bore hole and arranged at a distance from the axis of the supporting disc, which through bore hole is filled in by the permanent magnet only up to a gradation of diameters serving as a stopping surface, while the remaining part of the through bore hole serves to correct mass imbalances and is filled in by a filling material which is lighter in comparison to the specific weight of the permanent magnet and the base body.
A supporting disc of this type is prior art in U.S. Pat. No. 5,675,964. Methods for correcting mass imbalances of the permanent magnet applied to the known supporting disc are described in this publication in many variations. In one variation, a compensatory balancing weight is arranged diametrically opposite the permanent magnet, while in another variation a correction of mass imbalances is achieved in that in the supporting disc, material from the base body is removed in the area of the permanent magnet, for example by means of extending a bore hole in which the permanent magnet is taken up.
It is known that spun yarns break for a variety of reasons during operation. When this happens, the already spun yarn end must be pieced, that is, joined again with the fibers fed into a hollow inner space of the open-end spinning rotor. This takes place in the case of many operating machines by starting up the previously stopped open-end spinning rotor. It is important hereby to know, at any given moment of the piecing process, at what speed the open-end spinning rotor is rotating. This happens in practice by means of non-contact sensoring of the actual speed of a supporting disc, which indirectly gives information on the actual speed of the open-end spinning rotor which is supported on the supporting disc pairs.
The known supporting disc according to the above mentioned U.S. Pat. No. 5,675,964 has the advantage in that one single permanent magnet is sufficient for non-contact speed monitoring, without fear of mass imbalances occurring during rotation of the supporting disc. In the case of the known supporting disc, a direct correction of mass imbalances is created, namely in the area of the permanent magnet itself. The disadvantage in the case of the known supporting disc, however, is that the permanent magnet is glued into the through bore hole, which is complicated in respect to its fabrication.
In the non-generic German published patent application 101 30 734, two permanent magnets are disclosed, which are diametrically disposed to one another in relation to the axis of the supporting disc, and are located on the transition area between the base body and the tire-like covering. This has the basic advantage in that the permanent magnets can be secured to the base body by means of the tire-like covering itself. No correction in mass imbalance in the area of the permanent magnets is provided. The through bore holes, which serve as take-up receptacles for the permanent magnets, do not have any gradation of diameters serving as stopping surfaces, and the through bore holes are completely filled out by the respective permanent magnets.
It is an object of the present invention to manufacture a supporting disc of the above mentioned type in a more production-friendly way, while using the advantage known in German published patent application 101 30 734, namely to use the tire-like covering for fastening the permanent magnet.
This object has been achieved in accordance with the present invention in that the permanent magnet is arranged in the transition area between base body and tire-like cover, and in that the part of the through bore hole not filled out by the permanent magnet is instead filled out by the tire-like cover.
The supporting disc according to the present invention has the advantage in that one permanent magnet is sufficient for the purpose of non-contact speed monitoring, whereby gluing of the permanent magnet in the through bore hole can be omitted, as, due to the provided position of the permanent magnet in the transition area between base body and the tire-like cover, the latter fills out the part of the through bore hole not filled out by the permanent magnet and thus fixes the permanent magnet.
In an embodiment of the present invention, the base body is provided on its outer circumference with an annular ring which anchors the tire-like cover, in which, however, in contrast to the known supporting disc, not only the through bore hole is located, but also the gradation of the diameter.
It can be provided for the purposes of the present invention, that the permanent magnets project out of the through bore hole on the side facing away from the gradation of diameters and is fixed in this area by the tire-like cover. It has been shown that it is favorable for the correction of mass imbalances when the gradation of diameters is located approximately in the center of the through bore hole.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings wherein.